Hacker’s guide to NAV

If you are contributing code to Network Administration Visualized, please read this first.

Contributing to NAV

Originally, NAV was a closed source project, initiated by the Norwegian University of Science and Technology (NTNU), and eventually sponsored by UNINETT on behalf of the Norwegian higher education community. In 2004, however, NTNU and UNINETT started distributing NAV under the GNU General Public License, making it a truly free software system.

While UNINETT and NTNU are still the main contributors to NAV, developing NAV to support the needs of the Norwegian higher education community, contributions from third parties is highly appreciated.

We communicate mainly through mailing lists, Launchpad, and the #nav IRC channel on FreeNode. At times, UNINETT also arranges workshops and gatherings for its customers: Norwegian universities, university colleges and research institutions.

To contribute:

Go to https://nav.uninett.no/ and

  • Join the mailing lists. The nav-dev mailing list in particular is for discussing NAV development. So far, this is a low traffic list. We can only hope this will change ;-)
  • Get a copy of the latest development sources by cloning the Mercurial repository at https://nav.uninett.no/hg/default/. Most new development takes place on this branch.
  • Take a look at the project reports from previous development projects at NTNU (NAVMe, NAVMore, tigaNAV and others) - design specifications and other useful bits of historic NAV information is mostly to be found in these. Unfortunately, some of the oldest project documentation is in Norwegian only. Do not hesitate to ask for help on the mailing lists.

If you wish to contribute code to the project, see the Submitting patches section.

Directory layout

A rough guide to the source tree:

Directory Description
bin/ NAV ‘binaries’; executable scripts and programs.
contrib/ User contributed NAV tools. NAV doesn’t depend on these, and any maintenance of them is left up to the original developers. We do not offer support for these tools.
doc/ User and developer documentation.
etc/ Example/initial configuration files.
htdocs/ Static media such as CSS stylesheets, images and JavaScript to be served by a webserver.
packages/ Stuff to help packaging NAV for various platforms, such as RedHat, CentOS, FreeBSD, Debian and soforth. Much of this is outdated today.
python/ Python source code.
sql/ SQL schema definitions and installation/sync tools.
templates/ Django HTML templates.
tests/ Automated tests.
tools/ Scripts for aiding in various development, build and release processes.

Development languages and frameworks

All NAV back-end code is written in Python. The web-based user interface is implemented using the Python-based Django framework. In addition, there is an increasing amount of **Javascript* in the web-based user interface.

If you wish to contribute something really useful that doesn’t use Python, we may consider including it in the contrib/ directory.

If YOU are willing to invest in porting some of the existing Java code to Python, then you will be celebrated as a NAV hero!

Coding style

NAV code adheres to the Python style guide documented in PEP 8. Conventions for writing good documentation strings (a.k.a. “docstrings”) are immortalized in PEP 257.

Much of the legacy NAV code was, however, written without using any specific guidelines for coding style. We are working to improve this, and will accept patches that clean existing code.

Python boilerplate headers

We will generally only accept code into NAV if it is licensed under GPL v2, but we may make individual exceptions for code licensed under compatible licenses. Each Python source code file should contain the following boilerplate at the top:

#
# Copyright (C) 2008,2009 Somebody
#
# This file is part of Network Administration Visualized (NAV).
#
# NAV is free software: you can redistribute it and/or modify it under the
# terms of the GNU General Public License version 2 as published by the Free
# Software Foundation.
#
# This program is distributed in the hope that it will be useful, but WITHOUT
# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
# FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
# more details.  You should have received a copy of the GNU General Public
# License along with NAV. If not, see <http://www.gnu.org/licenses/>.
#

If a file uses non-ASCII characters, it must be encoded as UTF-8, and an encoding statement should be inserted at the top:

# -*- coding: utf-8 -*-

Javascript

When writing Javascript code, try to focus on modules, not pages. If the code is HTML-related, it should take selectors or objects as input and concern itself solely about those. This makes for much easier testing and reuse. And of course - write the tests first.

When the module is done you write a controller for the page that plugs the needed plugins to the page elements. This should fail gracefully if the needed elements are not present.

NAV’s Javascript uses RequireJS - use this to create modules and specify dependencies.

Pro tip is to create require_config.dev.js in htdocs/js/` and add the following configuration to RequireJS:

require.urlArgs = "bust=" +  (new Date()).getTime();

This makes sure your not using cached resources in your browser when developing, something browsers love to do! See config-urlArgs in the RequireJS documentation for details. require_config.dev.js is listed in the repository .hgignore file.

Database

NAV uses PostgreSQL as its database backend. Namespaces (schemas) are employed to logically group tables and relations. NAV versions prior to 3.5 employed separate PostgreSQL databases instead of namespaces.

The namespaces currently in use are:

Namespace Description
manage The core knowledge database of NAV, containing all sorts of information about the monitored IP Devices, events, alerts, network topology and machine tracking data.
profiles Contains NAV user accounts and groups, user preferences and alert profiles.
logger Anything related to NAV’s syslog parser/browser system.
arnold The port detention system Arnold stores it’s data here.
radius Radius accounting logs, updated directly by FreeRadius’ PostgreSQL module.

Connecting to the database (Python)

Raw SQL

To obtain a connection to the NAV database, use the API accordingly, e.g.:

import nav.db
# Get a connection to the NAV database
connection = nav.db.getConnection('default')

The above code will open a connection to NAV’s database, or, if a previous connection with these parameters is already open, returns the already existing connection from a connection cache.

The default parameter is there for legacy reasons; it specifies the name of a subsystem. The db.conf file allows configuration of separate database users for each subsystem (known as a script in db.conf) of NAV. The default db.conf file specifies a database user for a subsystem called default, and also specifies the same database user for all known subsystem names. At present, using a subsystem name that is not configured in db.conf will cause nav.db.getConnection() to revert to using the default name.

Django models

NAV 3.5 and on includes Django models for most database tables. If no SQL magic is needed to perform your database voodoo, it is recommended that you use these models, located in the module ‘’nav.models’‘. You do not need to explicitly establish a database connection to use these models, as Django takes care of all that.

The models are defined in modules of the ‘’nav.models’’ package.

Changing the schema

The baseline schema is located in sql/baseline/ - the navsyncdb program is responsible for running this when creating a new database. To make a schema change, you do not change the baseline, but go to the sql/changes/ directory and create a new schema change script there.

Schema change scripts as numbered, using the following pattern:

sc.<major>.<minor>.<point>.sql

The <major> and <minor> numbers usually correspond to the major and minor number of the next NAV release. The <point> number is a sequence id - pick the next free number when creating a schema change script.

Remember these points when creating a schema change script:

  • Create separate change scripts for unrelated schema changes.
  • Remember to write SQL to migrate existing data, if necessary.
  • Do not use transactional statements - navsyncdb will take care of that.

To apply your change scripts, just run navsyncdb. It will look inside the schema_change_log table to see which change scripts have already been applied, and it will detect your new change script and apply this to the database.

Note

When changing the schema, don’t forget to update the Django models in the nav.models package. An integration test exists to verify that the Django models can at least be used to run proper SELECT statements against the database.

Version Control

NAV uses Mercurial for distributed version control. Official repositories are located at https://nav.uninett.no/hg/ .

Trunk (default)

New, bleeding edge development occurs on the default branch and published to the http://nav.uninett.no/hg/default/ repository.

Feature branches

The default repository is mirrored on Bitbucket. If you go to the nav-mirror repository, you can fork it there and use Bitbucket to submit pull requests for us to review.

Stable

Once we are nearing a new series release of NAV (such as 4.2 or 4.3), a new named series branch is created from the default branch (This branch is named 4.3.x in the case of the 4.3 series of NAV).

Once this branch is stabilized, the first version is tagged and released. After this point, we accept only bug fixes in this branch. Further point releases in this series are tagged on this branch, and all changes are merged back onto the default branch.

The repository published at https://nav.uninett.no/hg/stable contains the latest stable series branch, and excludes the latest trunk developments you can find in the default repository.

When someone writes a patch for a bug, this should usually be committed to the latest active series branch which is affected by the bug. Once a new series is released, we do not usually maintain the older series branches. We may push bug fixes to these branches, but we are unlikely to create a new point release from it.

Push access

Push access to the official repositories is limited to developers employed or commissioned by UNINETT.

Testing and Continuous Integration

Much of NAV is legacy code, as defined by Michael C. Feathers: “Code that has no tests”. We have been making an effort to introduce automated tests into the codebase the past several years, and hope to improve coverage over time.

All test suites (except those for Javascript) are located in the tests/ subdirectory.

Running tests

We use pytest to run the test suite. A bundled version is included as runtests.py in the python/ subdirectory, and is used to run the unit tests only when a make check command is issued in the python/ subdirectory.

There’s also a script to produce an entire test environment as a Docker image and to run the entire test suite inside a Docker container created from that image. This is actually the same method employed by our Jenkins build servers to run the test suite. Take a look in the tests/docker/ directory.

Javascript testing

Testing javascript in NAV is straightforward. We use Karma as a testrunner, Mocha as testing framework and Chai as assertion library.

cd htdocs/static/js

# Install required libs, you need npm installed
npm install --optional

# Run tests. This will start browsers. Karma will make sure that tests will
# run on changes in js-files.
./node_modules/karma/bin/karma start test/karma.conf.js

All tests are located under htdocs/statis/js/test/. Create new tests there. For syntax, assertions and related stuff take a look at the tests already there and the relevant documentation linked above.

Jenkins

We use Jenkins (formerly Hudson) for Continuous Integration testing of NAV. All the automated tests are run each time new changesets are pushed to the official NAV repositories. Jenkins also runs pylint to create stats on code quality.

Our Jenkins installation is available on https://ci.nav.uninett.no/ .

Tips and tricks

Make fixtures for integration testing

from django.core import serializers
from nav.models.manage import Netbox

fixtures = serializers.serialize("xml", Netbox.objects.all()[:2])

Fixtures can so be used in your integration tests by extending the test case DjangoTransactionTestCase in nav.tests.cases.

See nav.tests.integration.l2trace_test for an example on applying fixtures for your particular test case.

See https://docs.djangoproject.com/en/1.4/topics/serialization/

Submitting patches

Unless you are submitting one-off fixes for bugs and small issues, please take the time to discuss your change proposals on the nav-dev mailing list. This will increase the chances of having your patches accepted.

Base your patches on the relevant Mercurial branches. If you are submitting a patch for an issue that affects the latest stable series, base your patch on that series branch (<major>.<minor>.x). If you are submitting patches containing new features, base them on the default branch.

The best way to submit your patches is to use Bitbucket: Fork our nav-mirror repository there and create a pull request for us to review.

Another option for a simple patch is to attach it to a Launchpad bug report.